Brian, Tom, List,
Libyan Desert glass is 98% pure silica, the
purest naturally discovered glass on Earth.
http://www.pisces-press.com/C-Nav/ldg.htm
While one sees as examples are clear, gem-like
LDG, many of the fragments found on the ground
(and tossed aside as "dirty" or not pretty enough)
are tabular and layered, clean, dirty, clean, dirty,
like the Muong-Nong tektites found in Laos
and Thailand.
Boslough at Sandia has a airburst theory...
naturally:
http://www.sandia.gov/news/publications/technology/2006/0804/glass.html
Most people think an impact origin. Too many
references to cite.
There are some completely dopey theories about
LDG, too. I found this one to be worth a good laugh:
http://www.b14643.de/Sahara/LDG/index.htm
And there are some people still think tektites
are volcanic:
http://www.rasc.ca/journal/pdfs/2004-10.pdf
Analysis of LDG can be found in Christian Koeberl,
"A Meteorite Component in LDG". He finds excess
cobalt, nickel, iridium:
http://www.lpi.usra.edu/meetings/metsoc2000/pdf/5253.pdf
Here's the actual earlier work by Koeberl, the full
paper, with complete data:
http://www.univie.ac.at/geochemistry/koeberl/publikation_list/132-Libyan-Desert-Glass-Proc-Bologna-Mtg-1997.pdf
Anyone have an idea why there's a ten-fold excess
of uranium in LDG? I'm sure that's spawned a few
whacko websites!
I quote from Koeberl "...none of the sands or sandstones
...are good candidates to be the sole precursors of LDG."
Formation temperature has to be high enough to melt
zircons, as they contain melted zircons (as many tektites
do). Ever tried to melt a natural zircon?
What is often missing from the discussions of the origins
of the LDG is the fact that the Libyian-Egyptian Desert pf
28.5 million years ago was NOT a desert. It was swamps,
vast lakes, bogs, and snaking bayous. What was not open
water was wet and very densely forested between 24 and
32 million years ago. The "Sahara" to the west and south
was grasslands and scattered forest.
Yeah, I know. Doesn't look it, does it? But in the Oligocene
Epoch it was more like the Amazon Basin on a smaller,
dryer scale. It's a rich source (only source, actually) of fossils
of early primate ancestors of apes and men. It seems to be
where we learned to hang out in trees (literally), the black
anaerobic crap underneath being something you didn't
want to fall into.
These wet basins were filled with hundreds of feet of
sand blown in from the west as the Sahara began to dry
out. This is the target geography that an impactor would
have struck. The high silica content pretty much has to
mean that LDG was made entirely from sand. The fact
that LDG is not as "dry" as most tektites may come from
the fact that the target soils were underwater some depth.
Merely geusses, though.
Is there a good book on tektites?
No. The study of tektites drives people crazy, and
crazy people do not write good books...
O'Keefe's 1976 "Tektites and Their Origins" book was
posted online for years but it's gone now. You can get
a copy on Amazon for $200. (O'Keefe was the "O" of the
"YORP Effect" or Yarkovsky-O'Keefe-Radzievskii-Paddock
Effect). Other books by Heinan and Provenmire are hard
to find. Now that I think of it... All books on tektites are
hard to find
Sterling K. Webb
-----------------------------------------------------------------------------
----- Original Message -----
From: <[email protected]>
To: <[email protected]>
Sent: Friday, August 27, 2010 10:20 AM
Subject: Re: [meteorite-list] Holbrook Tektites ( HEAT TESTING of
TEKTITES)
Very well done Brian! Thanks for sharing your results.
Your experience with the LDG, " Libyan Desert Glass - we took it up
to
1,815 Centigrade / 3,300
Degrees Fahrenheit and it was tacky on the surface , BUT did not
Melt"
This made me wonder again what others think of the idea that LDG is a
glass
meteorite and not a glass created in the same manor as most tektites.
This is not original thinking on my part as I have heard it proposed
as one of
the theories on LDG.
Any thought on this?
Some samples of LDG are shaped more like a meteorite than a tektite
aside
from the fact that they are glass!
Tom
In a message dated 8/27/2010 3:24:13 A.M. Mountain Daylight Time,
[email protected] writes:
Greetings to Dennis, Mark and List Members
HEAT TESTING OF TEKTITE
Aubrey has some good & interesting observations concerning Testing
Tektites on his sight
http://www.tektites.co.uk/tektite-tests.html
Personally , I have access to professional Glass Blowers with tons of
experience.. They work with Common , Borosilicate ( Pyrex ) and
Dichroic Glasses.
All types of Glass have different melting temperatures , and working
together with the Top Production planner ( Brent ) who is versed in
Heats and Flames required for melting these various types of glass,
we set about to Heat Test Several Types of Tektite. Temperature is
KEY to observations. Brent was aware of our goals and took time to
test various temperatures as well as using test pieces and had far
more information than I am able to convey simply. Lets just say that
Coefficient of Expansion, Coloration and other physical properties
were also in question during our tests.
Glass melts at a relatively LOW Temperature, about 485 Centigrade
/ 900 Degrees Fahrenheit ( Varies with the amount and types of
Alloys in the glass )
Bolorsilicate ( Pyrex ) at about 820 Centigrade / 1,510 Degrees
Fahrenheit
Thailandites, Philippinite , Moldavite and Quartz Glass melt at
about 1,665 Centigrade / 3,029 Degrees Fahrenheit
Libyan Desert Glass - we took it up to 1,815 Centigrade / 3,300
Degrees Fahrenheit and it was tacky on the surface , BUT did not
Melt, as my friend stated "it is laughing at us"... We are still
looking for a hotter Hydrogen Flame Unit to see what the actual
melting point is.
Darwin Glass - I have yet to test it, I forgot to bring samples.
Maybe
soon...
Obsidian explodes when heated quickly.
SO - it is easy to eliminate an Obsidian as a Tektite , just by
throwing alot of heat at it quickly.
Glass and Borosilicate varies from Tektites , easily, by applying
heat to samples of each set side by side, see what melts first ..
Don't worry about destroying the Tektite , it will be safe since the
glass will melt much sooner than any tektite, and if the Tektite
melts at the same temperature as Glass ?? It was not a Tektite.
Quartz Glass is rare and to find a piece while looking for Tektites
is just to unlikely to ever happen.
The reason Tektites can withstand such High Heat is that the
impurities that allow Glass to melt at lower temperatures have been
Burnt out of them already.
MY THEORY:
Thailandites, Philippinite and Darwin Glass have coloration from the
residue left by these Burnt off elements. Heavily contaminated.
Moldavite also gets its coloration from the Burnt off elements. Less
Contamination
Libyan Desert Glass is very clean and was intensely heated to remove
even the residual left by burning off impurities. Minimal
Contamination.
Highest Regards to All
Brian S. IMCA # 7381
http://stores.ebay.ca/AAJEWELCOM
------------------------------
Date: Thu, 26 Aug 2010 13:15:36 -0400
From: <[email protected]>
Subject: Re: [meteorite-list] Holbrook Tektites ( Magnet canes are
evil)
To: [email protected], Dennis Miller
<[email protected]>, Mark Bowling <[email protected]>
Dennis, Mark,List,
Interesting you mention finding rocks that resemble certain
tektites. You describe them as looking translucent and weathered
with a tektite texture.
Years ago I found what I thought was a strewnfield of tektites in
Southern AZ.
They too looked like what you found.
I took them to ASU and Dr. Moore had his assistant attempt to melt
one of them.
He explained that a true tektite would simply melt like glass
similar to the way a glass blower melts glass.
If however it gets frothy and white it is not a tektite but likely
natural obsidian glass. This had something to do with the amount of
water. Apparently tektites are much dryer than obsidian.
Well, they tested frothy and therefore deemed to be sand blasted
obsidian. I believe he also said they are not magnetic. Some of mine
were magnetic others were not.
Curiously, I have since found that Surf-tumbled Sea glass has
exactly the same appearance as these sand blasted obsidian orbs I
found in the desert. The only difference is that sea glass does melt
like tektites so, the melting test does not work on them.
In fact other than the flanged buttons, to me many of the "Tektites"
look more like Sea-glass than anything else.
If you are unaware of it. Sea glass is largely a product of surf
tumbled glass that has been littered or discarded by human activity
in the past.
If you Google it there are lots of people selling it.
What I found looks like either Columbianite or Georgia Tektite. two
different looking types all in the same find area.
Really Makes me wonder about the true origin of Tektites.
Carl
--
Carl or Debbie Esparza
Meteoritemax
---- Mark Bowling <[email protected]> wrote:
> Dennis,
> I have found?tiny glass spherules in some areas along the tracks -
lots of
> them.? I think it's welding slag from RR operations.? I was
pretty excited until
> someone suggested it (I never had them tested, but?hard to
believe folks would
> overlook something significant until me...).?
> Nothing as big as you mention (other than the marbles we
> occasionally
> find).???In other places I?have found weathered obsidian which
> often
has a
> tektite texture (though not the same).? I think it's caused by
> solution
> weathering.
> I have a magnet cane, but I never used it to pick up a
meteorite.? It's just a
> fashion statement I guess (peer pressure).? ;-)
>
> Mark B.
> Vail, AZ
>
> ----- Original Message ----
> From: Dennis Miller <[email protected]>
> To: [email protected]
> Sent: Tue, August 24, 2010 3:08:13 PM
> Subject: [meteorite-list] FW: Magnet canes are evil
>
> > My modified ski pole (with Magnet) is more a walking stick and
snake flipper!
> > I have a question, Has anyone ever found small tektites around
the Holbrook?
> > I know if there were, that they were not the result of the
Holbrook splatter.
> > While there Sunday, I found what is either an egg shaped (5/8")
obsidian ball
> > or a tektite of sort. Light will pass through it but it has an
unusual
> textured skin. I have seen a lot of Apache tears (obsidian orbs)
but none like this little guy.
> > Carrying a big stick at all times.
> > Dennis Miller
> >
> >
> > > Date: Tue, 24 Aug 2010 10:10:10 -0700
> > > From: [email protected]
> > > To: [email protected]
> > > Subject: [meteorite-list] Magnet canes are evil
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